Machine tool



April 15', 1958 R. c. NoRTHcuTT 2,830,409

MACHINE TOOL Filed Dec. 14. 1955 as@ /////////////QV53 jaa United States Patent O MACHINE TOOL Roy C. Northcutt, Muncie, Ind., assignor to Borg-Warner Corporation, Chicago, lll., a corporation of Illinois Application December 14, 1955, Serial No. 553,005

3 Claims. (Cl. 51-50) My invention relates to grinding machines, and more particularly to grinding machines of the typ for grinding workpieces internally.

A grinding machine of this type generally'comprises a main supporting bed, a workhead mounted on the supporting bed comprising a motor and a chuck driven thereby for holding and driving a workpiece, and a wheelhead also mounted on the supporting bed comprising a motor and a grinder wheel mounted thereon and driven thereby, the workhead being capable of being moved transversely of the bed so .that the workpiece may be moved into contact with the grinder wheel to take off more and more stock.

In the machines of this type, prior to my invention, the workhead was mounted on the main bed by two parallel' anti-friction bearings, called cross-slide bearings, which allowed transverse movement of the workhead with respect to the main bed. These bearings each included a race on the workhead and a race on the main bed and steel balls between the races. When the machine was in operation, the steel balls were subjected to loads in both the vertical and horizontal directions. As the workhead moved transversely with respect to the bed under these vertical and horizontal loads, the steel balls tended to simultaneously rotate above vertical and horizontal axes. Since this was impossible, the result was that the balls slipped for either the vertical load or the horizontal load. In a relatively short period of time, this sliding and the large loads wore indentations in the races which resulted in irregular bearings and inaccuracies in grinding.

It is an object of the present invention to substantially increase the durability of the grinding machine and to enable it to maintain its accuracy over a much longer period of time.

It is another object of the present invention to provide improved cross-slide bearings for use in lieu of the bearings with steel balls mentioned above and which will take the horizontal and vertical loads on the workhead with only negligible wear to the bearing races.

It is an additional, morefparticular, object of the invention to construct the bearings of cylindrical steel rollers some with their axes disposed at right angles to the others, so that some will roll and support the horizontal loads, and the others will roll and support the vertical loads. Still more particularly, it is an object of the invention to disposealternate ones of the rollers with their axes vertical and the others of the rollers with their axes horizontal.

It is another object of the invention to maintain uniform spacing of the rollers by means of diagonally extending retainers. These retainers are preferably constructed of at strips of metal, or other suitable material, with slots therein for diagonally enclosing the rollers around tapered ends provided on the rollers.

The invention consists of the novel constructions, arrangements vand devices to be hereinafter described and 2,830,409 Patented Apr. 15, 1958 ICC claimed for carrying out the above-stated objects and such other objects as will appear from the following description of a preferred embodiment of the invention, illustrated with reference to the accompanying drawings, wherein:

Fig. l is a diagrammatic side view of an internal grinding machine embodying the principles of the invention;

Fig. 2 is a sectional view on an enlarged scale of the cross-slide bearing of the grinding machine taken from lines 2-2 of Fig. 1;

Fig. 3 is a sectional view taken on line 3-3 on Fig. 2 in the direction indicated;

Fig. 4 is a sectional view taken on line 4-4 of Fig. 3 in the direction indicated; and

Fig. 5 is a view showing the roller retainer and a plurality of rollers therein and being taken on line 5-5 of Fig. 3 in the direction indicated.

Like characters of reference designate like parts in the several views.

Referring to the drawings, the illustrated internal grinding machine 10 comprises a main supporting bed 11 upon which is mounted two longitudinally extending horizontal rails 12 supporting a wheelhead 13 on one end. The wheelhead 13 comprises an electric motor 14, a spindle 15, and a grinder wheel 16. The wheelhead 13 can be moved horizontally along the rails 12. A workhead 17 is mounted on the other end of the main bed 11 and comprises an electric motor 18 and a chuck 19 for holding a workpiece 20 having a cylindrical aperture 21 therein, the inside wall of which is to beground.

A workhead carriage 22 carrying the workhead 17 is movably mounted with respect to the bed 1l by two bearings 23 and 24. These bearings allow the workhead to be moved horizontally in a direction transverse to the main supporting rails 12, and any suitable means can be provided for moving the workhead 17 transversely including an adjusting wheel 25 for turning an adjusting screw 26. The bearings 23 and 24 between the carriage 22 and the bed 11 minimize the friction between the carriage 22 and the bed 11 and at the same time rigidly hold the workhead 17 against any undesired vertical or horizontal movement.

The front bearing 23 comprises rollers 27 and 28, a lower rail 29 and an upper rail 30. The upper rail 30 is made up of a main body 31 and an end piece 32 which is fastened to the main body 31 by means of machine screws 33. The lower rail 29 is provided with horizontal race surfaces 34 and 35 and vertical race surfaces 36 and 37 on opposite sides of the rail. The upper rail 30 is provided with horizontal race surfaces 38 and 39 opposite the rail surfaces 34 and 35 respectively, and vertical race surfaces 40 and 41 opposite the race surfaces 36 and 37 respectively.

The rollers 27 and 28 in physical dimensions are identical and have, respectively, cylindrical surfaces 42 and 43, end surfaces 44 and 45, and tapered surfaces 46 and 47. The rollers 27 are alternately disposed with respect to the rollers 28 between the rails 29 and 30, and the axes of rotation of the rollers 27 are horizontal and parallel to the main bed 11 of the grinder 10. The rolling surfaces 42 of the rollers 27 on the left side of the rail 29 are in contact with the race surface 34 of the rail 29 and the race surface 38 of the rail 30. The rolling surfaces 42 of the rollers 27 on the right side of the rail 29 are in contact with the surface 35 of the rail 29 and the surface 39 of the rail 30. The rollers 28 have their axes of rotation vertical and have their rolling surfaces 43 in contact with the surface 36 of the rail 29 and the surface 40 of the rail 30 on the left and in contact with the sur- 0 face 37 of the rail 29 and the surface 41 of the rail 3 which is in the direction the workhead 17 was designed l to move, namely, transversely of the main bed 11. The i axial lengths of the rollers 27 and 28 are slightly less than their rolling diameters; and with the rollers 27 and 28 disposed as shown, there s a slight clearance between the liat ends 44 of the rollers 27 and the adjacent race surfaces 36 and 40 on the left and 37 and 41 on the right. There will also be clearance between the iiat ends 45 of the rollers 28 and the surfaces 38 and 39. This clearance in each case is shown exaggerated for the purpose of illustration.

Bearing retainers 48 and 49 maintain the uniform spacing of the rollers 27 and 28. The retainers are identical and are constructed of a flat strip of metal or other suitable .stn'p material having a series of partially semicircular elongated slots 50 therein. The bearing retainers 48 and 49 extend diagonally across the rollers 27 and 28. The retainer 48 rests on diagonally extending surfaces 51 and 52, and the retainer 49 rests on similar slanted surfaces 53 and 54. The slots 50 are of such shape as to partially encircle the rollers 27 and 28 and hold them -spaced at xed distances from each other. As will be apparent, the retainers are free to move when the workhead 17 is moved transversely of the bed 11, and the rollers 27 and 28 are free to rotate within the slots 50.

Ihe rear bearing 24 of the grinding machine 16 can be any flat race bearing of suitable construction. This bearing 24 supports only vertical loads, because all horizontal loads upon the workhead 17 are taken by the front cross-slide bearing 23 and the screw 26.

In operation the machine is used as follows:

The workpiece 20 is placed in the chuck 19, and when the motor 18 is energized, the workpiece 20 is rotated about a horizontal axis. The wheel head 13 is moved horizontally along the rails 12 by any suitable means until the grinder wheel 16 is inside the aperture 21 of the workpiece 20 with the motor 14 driving the grinder wheel 16. The wall of the aperture 21 in the workpiece 20 is brought into contact with the grinder wheel 16 by moving the workhead 17 transversely on the bearings 23 and 24 as by rotating the adjusting wheel 25 and screw 26. This initial movement may be made relatively fast, and when the grinder wheel 16 actually contacts the wall of the aperture 2l, thereafter the transverse motion of the workhead 17 is relatively slow. The transverse motion of the workhead 17 is continued until the desired amount of stock is removed from the interior of the workpiece 20.

As will be understood, there is a downward force on the bear-ings 23 and 24 which is due to the weight' of the head 17 and the carriage 22 and there is also an upward or downward force depending on the relative direction of rotation due to the grinding action of the grinder wheel `16 on the workpiece 20. In the bearing 23, the rollers 27 which are disposed to rotate about horizontal axes, take the downward load. The rolling action is between the at raceway surface 34 of the rail 29 and the flat surface 38 of the rail 30, and also between surface 35 of the rail 29 and the surface 39 of the rail 30. There is also a horizontal force on the head 17 longitudinal of the bed 11 due to the grinding action, and the rollers 28, which are disposed to rotate about vertical axes, take the 'load in this direction. The rolling action in this case is between the vertical race surface 36 of the rail 29 and the surface 40 of the rail 30, and also between the surface 37 of the rail 29 and the surface 4l of the rail 30. Sincev the horizontally disposed rollers are not in contact with the vertical raceway surfaces, and the vertically disposed rollers have their end surfaces out of contact with the horizontal raceway surfaces, there is no vertical or horizontal binding without rolling movement of the rollers 27 and 28 within the races. The retainers 48 and 49 function to maintain the uniform spacing of the rollers 27 and 28 and allow them to rotate freely.

The rollers 27 and 28, which are respectively disposed to rotate about horizontal and vertical axes, advantageously provide the rolling action between the upper and lower races of thebearing' 23, and at the same time, take the downward load and also the load longitudinal of the bed 11 without binding action on the rollers. Any bearing wear, as compared with that using bearings with steel balls as in prior constructions, is practically eliminated. This latter advantage is particularly due to the fact that the cylindrical bearing rollers 27 and 28 distribute the load over lines of contact with the race surfaces, instead of distributing the load over only points of contact as did the steel ball bearings. This latter advantage is also due to the fact that there is no force on any of the rolling elements in my improved construction tending to rotate them about any more than one axis at the same time; and, therefore, there is no frictional rubbing action between the rolling elements and their raceways to cause undue wear.

I wish it to be 'understood that my invention is not to be limited to the specific constructions, arrangements and devices shown and described except only insofar as the claims may be so limited, as it will be understood to those skilled in the art, that changes may be made without departing from the principles of the invention.

I claim:

l. In a machine for machining a workpiece element; the combination of a main supporting bed for the machine; two heads supported on said bed; one of said heads having a device for gripping the workpiece element and the other of said heads having a tool element for removing material from the workpiece element; a motor associated with one of said heads for driving the said element carried thereby; a bearing between one of said heads and said main bed for allowing movement of said lastnamed head as said workpiece element has material removed from it by said tool element; said bearing comprising two parallel horizontal raceway surfaces facing each other and two parallel vertical raceway surfaces facing each other and between said horizontal raceway surfaces, a series of rollers disposed to rotate about horizontal axes and having cylindrical rolling surfaces in contact with said horizontal raceway surfaces and a series of rollers alternately disposed with respect to said first named rollers and disposed to rotate about vertical axes and having cylindrical rolling surfaces in contact with saidvertical raceway surfaces, each of said rollers having tapered end surfaces on the edge of its cylindrical rolling surface, and a retainer for said rollers for holding them spaced with respect to each other and comprising a strip having slots therethrough for receiving said rollers, said strip extending diagonally with respect to said horizontal and vertical raceway surfaces and being in contact with said rollers on a said tapered end surface of each of the rollers.

2. In a machine tool, the combination of a main supporting bed, a head disposed on said bed, and a bearing structure disposed between said head and said bed for allowing relative movement therebetween, said bearing structure comprising a first pair of parallel facing raceway surfaces one on said bed and one on said head, a second pair of parallel facing raceway surfaces one on said bed and one on said head and adjacent to and disposed at right angles with respect to said first surfaces, the edges of said surfaces defining slots between said bed and said head, a first series of rollers disposed between said first raceway surfaces and having cylindrical rolling surfaces in contact therewith, a second series of rollers disposed at right angles with respect to rst rollers and. having cylindrical rolling surfaces in contact with said second raceway surfaces, and a retainer for said rollers for holding them spaced with respectto each other and comprising a strip having slots therethrough for receiving said rollers, said strip extending diagonally withrespect to the surfaces through the slots dened between said head and said bed.

3. In a machine tool; the combination of a main supporting bed; a head disposed on said bed; and a bearing structure disposed between said head and said bed for 5 allowing relative movementtherebetween; said bearing structure having two extended parallel bearings each comprising a rst pair of parallel facing raceway surfaces one on said head and one on said bed, a second pair of end surfaces on the edges of its cylindrical rolling surfaces, and a retainer for said rollers for holding them spaced with respect to each other and extending through the slots defined between said head and said-bed and being in contact with said rollers on a tapered end surface of each of said rollers, said two bearings respectively holding said head from lateral movement on said bed in opposite directions and allowing movement of said head with respect to said bed in directions at right angles parallel facing raceway surfaces one on said head and 10 thereto.

one on said bed and adjacent to and disposed at right angles with respect to said first surfaces, the edges of said surfaces defining slots between said head and said bed, a lrst series of rollers disposed between said first raceway surfaces and having cylindrical rolling surfaces in 15 2,230,442

contact therewith, a second series of rollers alternately disposed with respect to said first named rollers and having cylindrical rolling surfaces in contact with said second raceway surfaces, each of said rollers having tapered References Cited in the le of this patent UNITED STATES PATENTS Arms Feb. 4, 1941 FOREIGN PATENTS 556,746 Great Britain oct zo, 1943 892,553 France Jan. l0, 1944 

